TDL (the data library) is a collection of python modules that support data processing, analysis and modeling. These modules are designed to run within a standard python environment, and should be importable into other python programs/environments. See e.g. Larch --> the next generation data processing environment.
The current status is that TDL has a substantial amount of code written for data handling, including spec data, image files, ctr data processing, xrf data processing, modeling x-ray reflectivity, simple crystallography computations etc...
Note that TDL is the name of the overall project. There are a number of different packages within this project. The documentation below should help you get started. There is additional documentation in the python source files, and by looking at the help options in the interactive shell or interface that you are using.
Please feel contribute to the code and documentation effort!